What’s Up in July: Planet pairs and meteors follow exciting transit

The first full month of summer will bring some interesting celestial sights with it, but nothing as dramatic as the transit of Venus we experienced last month.

Most of Maine got extremely lucky as the skies finally cleared after a solid week of rain just minutes before the great event was due to start. I was well prepared by having a live feed from Mauna Kea in Hawaii projected onto a large screen in York Harbor for a reunion of the class of 1957 from MIT. We also had an 8-inch Dobsonian telescope with solar filters ready to go, though we didn’t think we would even use it until a few minutes before the transit started at 6 p.m.

Additional Photos

SKY GUIDE: This chart represents the sky as it appears over Maine during July. The stars are shown as they appear at 10:30 p.m. early in the month, at 9:30 p.m. at midmonth and at 8:30 p.m. at month’s end. Saturn and Mars are shown in their midmonth positions. To use the map, hold it vertically and turn it so the direction you are facing is at the bottom. Sky Chart prepared by George Ayers

It was interesting to see that the transit started about nine minutes earlier for us in Maine than it did in Hawaii. It was a very dramatic beginning because we were still fighting some clouds as Venus played hide and seek for about half an hour. The clouds racing across the sun added a nice three-dimensional view of the whole scene, giving it more excitement. Then we watched and photographed it through the telescope along with the live feed from Hawaii while we enjoyed a lobster and clambake for the next two hours until the sun set.

I watched the entire event until nearly 1 a.m. from different live feeds across the world. Some of the telescopes had hydrogen alpha filters, so I could also see the red prominences around the sun. There were also about 10 large sunspots on the active sun during this transit, which you can see anytime with just a good solar filter and a pair of binoculars.

Even though we don’t need accurate timings of the transit to determine the solar size and distance anymore, there are still many things we can learn today from carefully watching such a rare event. I got a much better sense of the vast size and power of our sun and the great scale of even the inner part of our solar system, which is the smallest part of it.

Venus orbits the sun at 22 miles per second, more than 3 miles per second faster than the Earth moves, and even at that great speed, it still took six and a half hours to complete the transit. Venus was 3 percent of the size of the sun, but it would only be 1 percent of the sun’s size if it were the same distance from us. Sometimes called our sister planet, Venus is about the same size as Earth, 8,000 miles in diameter.

I was able to see the black drop effect during both the beginning and ending of this transit, but I did not see the silvery semicircular arc of the heavy atmosphere of Venus starkly outlined against the blackness of space. Fortunately, I saw the silver arc last time, during the end of the transit on the morning of June 8, 2004.

The next transit won’t occur until December 2117. However, there will be a less dramatic transit of Mercury on May 9, 2016. These happen 13 times per century.

A really dramatic event that would let you see the entire inner solar system at once is a simultaneous transit of Mercury and Venus. That last happened more than 375,000 years ago and will next happen in the year 69,163.

The most important thing to remember is that you don’t need to actually see any of these events for yourself to know about them and their potential to happen. Just like lunar or solar eclipses or northern lights or active meteor showers, these events allow us a brief glimpse of the real inner workings of our solar system. We can’t see them all the time because of our very limited Earth-bound perspective.

For me, this last transit of Venus was only a very small part of a great ongoing lesson in applied math and physics, art, philosophy, music and general solar system appreciation.

The events for next month include a nice pair of planets in the evening sky and another pair of planets in the morning sky. There will also be a meteor shower on July 28.

Now that Venus has crossed over the sun, Mars and Saturn are the only remaining evening planets. They are both in Virgo now, and orange Mars is rapidly catching up with golden Saturn at the rate of half a degree per day. They start the month 24 degrees apart and end just 8 degrees apart.

Keep watching this pair into mid-August, when Mars will glide between Saturn and the nearby bright star Spica for a wonderful triple conjunction.

The two brightest planets, Venus and Jupiter, will be close together in the morning sky for the rest of the summer. Look low in the eastern sky one hour before sunrise. Venus will be right next to Aldebaran, which marks the eye of Taurus, on July 10. Jupiter will be above it, halfway to the Pleiades. Then watch as a slender waning crescent moon glides right between the pair on the mornings of July 14 through July 16.

The annual Delta Aquarid meteor shower will peak on the morning of July 28, but the nearly full moon will wash out most of them. Probably caused by Comet 96P Macholz, this shower is usually much better in the southern hemisphere.

The radiant of this shower, the point from which all of these meteors will appear to originate, is in Aquarius, just above the famous star called Fomalhaut.

Located 25 light years away, this is a very important star because the first exoplanet ever directly seen with visible light, instead of just by its effect on its parent star, was discovered by the Hubble Space Telescope orbiting this star just four years ago. It is probably only about twice the size of Earth and it orbits just inside a vast dust ring that extends over 120 times the Earth-sun distance from the star.

This planet, named Fomalhaut b, is very young at about 100 million years old, and was the first planet since Neptune to actually be found after it was first predicted to exist.

Just by coincidence, Neptune is also in Aquarius right now and it will have completed only one orbit since it was discovered in 1846. Neptune takes 165 years to orbit the sun. Its discovery is a fascinating story involving nine astronomers from three countries.

I have seen this ethereal blue planet, the last one in our solar system, several times through a telescope.

JULY HIGHLIGHTS

•July 3. Full moon is at 2:52 p.m. EDT. This is also called the hay or thunder moon.

•July 4. The Crab nebula in Taurus exploded on this day in 1054. It was independently witnessed and recorded around the world. The Earth is at aphelion, or farthest from the sun today. It is only 3.3 percent farther away now than it will be on Jan. 4.

•July 6. Isaac Newton’s Principia was published on this day in 1687.

•July 10. Last quarter moon is at 9:49 p.m.

• July 15. The moon forms a nice quadrangle with Venus, Aldebaran and Jupiter this morning.

•July 16. Apollo 11 was launched to the moon on a Saturn 5 rocket today in 1969.

• July 19. New moon is at 12:24 a.m.

•July 20. The first humans set foot on the moon on this day in 1969.

•July 21. The space shuttle program ended on this day last year. It lasted for 30 years and 135 launches. The shuttles traveled about 500 million miles or all the way to Jupiter. They made over 21,000 orbits around the Earth and spent 1,333 days in orbit.

•July 23. The Chandra X-ray observatory was launched on this day in 1999 aboard the Columbia.

•July 24. Look low in the western sky one hour after sunset for another quadrangle of celestial objects. This time it will be the moon, Spica, Saturn and Mars.

•July 26. First quarter moon is at 4:56 a.m.

• July 28. The Delta Aquarid meteor shower peaks. Also look for some early Perseid meteors.

Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.

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